Polymerisation method, polymers and uses thereof

ABSTRACT

Monomers (e.g. thinphenes) are caused to polymerise by mixing them with an oxidising agent (and generally a solvent comprising water) and irradiating the mixture with light (visible or UV). Polymer properties can be varied by doping or chemical modification. Uses include sensor elements for assays and electrical components such as electrodes.

TECHNICAL FIELD

The present invention relates to a polymerisation method, polymers and uses thereof. It is particularly but not exclusively concerned with a method for photochemical polymerisation of monomers using an aqueous, organic or water-organic mixed environment, and with applications of this method and of polymers formed thereby. Material synthesised in this way may comprise diners, oligomers, polymers, and mixtures. They may be grafted to the illuminated surface during polymerisation or collected from solution and used afterwards. Polymers prepared as described above or materials coated with polymer may be used in many fields, e.g. analytical chemistry (sensors, assays), electronics, optical and electrooptical devices.

The polymerisation of thiophene derivatives in water is an area of particular interest. Until now there has been an absence of reproducible methods giving high yields of polymer.

BACKGROUND ART

Patent Inventor (s) Issued Title US4717673 Wrighton et  1/1988 Microelectrochemical devices. al. US4729851 Brainling  3/1988 Polymers with conjugated double bonds. US4585581 Skotheim  4/1986 Polymer blends for use in photoelectrochemical cells for conversion of solar energy to electricity US4804594 Jow et al.  2/1989 Predoped conductive polymers as battery electrode materials. US5188766 Eiffler  3/1990 Electrically conductive polymer compositions, processes and polymers useful for preparing the polymer compositions. US4986886 Wei et al.  5/1990 Polymerization of thiophene and its derivatives US4731311 Suzuki et 10/1986 Electrically conductive al. material and secondary battery using the electrically conductive material US5106690 Stramel et 12/1990 Method for producing al. electrically conductive pigmentary composites US5198153 Angelopoulos  5/1989 Electrically conductive et al. polymeric US5370825 Angelopoulos  3/1993 Water-soluble electrically et al. conducting polymers, their synthesis and use US4954414 Adair et al.  9/1990 Photosensitive composition containing a transition metal complex cation and a borate anion and photosensitive materials employing the same

JOURNAL LITERATURE

-   Bryce et al. Soluble, conducting polymers from 3-substituted     thiophenes and pyrroles. J. Chem. Soc. Chem. Commun., 466-467, 1987. -   Sato et al. Soluble conducting polymers by electrochemical     polymerization of thiophenes having long alkyl substituents.     Synthetic Metals, 18, 229-232, 1987.

DISCLOSURE OF INVENTION

The present invention relates to the polymerisation of monomers. It is primarily concerned with monomers susceptible to radical and/or oxidative polymerisation. Monomers to be polymerised may comprise one or more types selected from paraphenylenevinylenes, anilines, azines, thiophenes, p-phenylenes, furanes, pyrroles, selenophenes, acetylenes and olefins, any of which may be substituted or unsubstituted.

The polymerisation system generally involves one or more solvents which may be aqueous, organic, or mixed aqueous-organic.

Thus the invention provides a method for preparation of a polymer comprising: a) mixing of monomers, oxidiser, and optionally solvent; and b) illuminating the mixture with visible or UV light.

In further aspects the invention provides polymers as prepared, directly or indirectly, by such a method; and uses of such polymers.

MODES FOR CARRYING OUT THE INVENTION

A preferred type of embodiment involves oxidative photopolymerisation of thiophene derivatives, in particular 3-thiopheneboronic and 3-thiophenecarboxylic acids. Reaction is performed in the presence of oxidising agent, preferably, potassium dichromate or copper (II) chloride. It is initiated by illumination with visible light. There is no sign of polymerisation observed in the dark. The mechanism of the reaction is not clear. Influence of pH of the solution (reaction rate drastically decreases at pH higher than 5.0) and chelating agents (cyclen, in 10 mM concentration decreases polymer formation by 15%) indicate a significant role of the acidic group and metal (particularly chromium ions from dichromate) in the polymerisation process. 3-Thiopheneboronic acid, esterified with diethanolamine was not polymerisable at all under the conditions described.

It is possible that there is radical formation in the process of thiophene oxidation, which can be stabilised by neighbouring acid groups. Illumination is a necessary key step for the chain growth. Chromium complexes are well known photocatalysts which are able to generate radicals (U.S. Pat. No. 4,954,414). Neither chromium (II) nor chromium (III) ions are able to initiate photopolymerisation of 3-thiopheneboronic acid in the absence of oxidising agent. Some polymer formation can be observed when chromium (III) is used together with ammonium persulfate. All these observations indicate that in order to polymerise thiophene derivatives the presence of both oxidiser and light is required.

The present invention can be employed for coating of surfaces with polymers, particularly polymerised thiophene derivatives. Practically any surface (e.g. glass, fluorocarbons such as ptfe (teflon), quartz, other synthetic polymers such as polyethylene, metals, etc.) can be coated by the polymer during the described process. The polymer can also be collected from the reaction and used subsequently in solution to coat the surfaces mentioned. The polymers can also be grafted to another polymer present in the solution during polymerisation.

Polymers embodying the invention may be used as coatings for microelectochemical and electrochemical devices. The polymer can be prepared in insulating or conducting forms, depending on polymerisation conditions. Depending on material properties and application required, the most important areas of the material utilisation are:

1) Electromagnetic shielding as protective materials in commercial and domestic applications.

2) Microwave protective shielding and filtering coatings for military and domestic applications (Stealth and Radar technologies).

3) Coatings of electronic components and devices for conducting purposes for use in eletrostatic dissipation in commercial and domestic applications.

4) Electroluminescent display devices, i.e. for organic LED's.

5) Use as photochromic materials for Smart Window technology.

6) Novel sensing materials in sensors and arrays, e.g. gas sensors and optical devices.

7) Use in solid state batteries as an environmentally friendly energy source.

8) Use in storage of solar energy.

9) Use in photorecording and photosensitive materials.

A polymer can be produced in the presence of a template material, which may be (a compound, a macromolecule or part of a biological system such as a cell or cell component (e.g. a cell wall or part thereof). The template material may then be removed so that the polymer has complementary cavities. It may then be capable of acting as a specific binding member for the template material. It may be useful in assays.

The properties of a polymer can be altered by doping (e.g. with iodine or an organic acid, which may be added to the mixture before polymerisation or afterwards) or by chemical modification (e.g. esterification, reduction, conjugation with other molecules, applied to the monomer or the product of polymerisation. The properties affected may be physical (e.g. solubility), optical or electrochemical (e.g. conductivity).

The synthesised polymers and polymer-coated articles may find use: (a) in microelectrochemical devices, e.g. as conductive or insulating layers, electrodes, contacts etc; (b) in capacitors for storage of solar energy or batteries, e.g. as electrodes or electrode coatings; (c) as electromagnetic and microwave interference coatings; (d) in electronic applications and fabrications, e.g. as conductive or insulating layers, electrodes, contacts etc; (e) as photorecording and photosensitive material; (f) in sensors and assays, e.g. as conductive or insulating layers, electrodes, contacts, detectors, immobilisation or sensitive matrices etc; (g) in optical and nonlinear optical devices, including electroluminescence devices; and (h) as protective materials.

Some examples below describe the polymer preparation, characterisation and possible application.

EXAMPLES

-   1) 2 ml of 0.1 M 3-thiopheneboronic acid in 50% water-ethanol     mixture was mixed with 2 ml of 0.2 M K₂Cr₂O₇ in water and     transferred to a polystyrene cuvette. Illumination with a 100 W     white lamp led to the formation of a brown pellet with simultaneous     grafting of the poly-thiopheneboronic acid to the polystyrene     surface. Poly-thiopheneboronic acid was collected and washed with     water, methanol and diethyl ether. After drying, the dark brown     pellet was pressed into a disk to measure the material's     conductivity. -   2) 2 ml of 0.1 M 3-thiophenecarboxylic acid in 50% water-ethanol     mixture was mixed with 2 ml of 0.2 M K₂Cr₂O₇ in water and     transferred to a polystyrene cuvette. Illumination with a 100 W     white lamp led to the formation of a brown pellet with simultaneous     grafting of the poly-thiophencarboxylic acid to the polystyrene     surface. Poly-thiophenecarboxylic acid was collected and washed with     water, cold methanol and diethyl ether. After drying the resulting     black pellet was pressed into a disk to measure the material     conductivity. -   3) 2 ml of 0.1 M 3-thiopheneboronic acid in 50% water-ethanol     mixture was mixed with 2 ml of 0.2 M CuCl₂ in water and transferred     to a polystyrene cuvette. Illumination with a 100 W white lamp led     to the formation of a brown pellet with simultaneous grafting of the     poly-thiopheneboronic acid to the polystyrene surface. Reaction was     10 times less effective in comparison with the one when K₂Cr₂O₇ was     used. Poly-thiopheneboronic acid was collected and washed with     water, methanol and diethyl ether. After drying, the dark brown     pellet was pressed into a disk to measure the material conductivity.     The polymers, prepared as described above have surface and volume     conductivity in the range of 10⁻² to 10¹ S/cm, depending on     polymerisation time and doping conditions. -   4) The cuvette coated with poly-thiopheneboronic acid was washed     with water and methanol. Coating was homogeneous and stable. In a     similar way a glass cuvette, microtiter reader plate wells and a     platinum electrode were coated with equal efficiency. -   5) The microtiter plates were coated with poly-thiopheneboronic     acid, prepared in the presence of atrazine. 50 μl of polymerisation     mixture containing 0.1 M 3-thiopheneboronic acid and 5 mM atrazine,     soluble in 50% water-ethanol mixture was transferred into the     microplate wells and mixed with 50 μl of 0.2 mM K₂Cr₂O₇.     Polymerisation was initiated by illumination with 100 W white lamp     for 1 hour. The microplate was washed with 5 mM HCl in methanol to     remove the atrazine and finally with methanol. Competitive assay     performed with horseradish peroxidase-atrazine conjugate and free     atrazine revealed high affinity of the atrazine-imprinted     poly-thiophene boronic acid to atrazine with dissociation constant     Kd=20 nM. 

1. Method for preparation of a polymer comprising: a) preparing a mixture by the mixing of monomers, oxidiser, and optionally a solvent; and b) illuminating said mixture with visible or UV light.
 2. Method according to claim 1 which employs an aqueous solvent.
 3. Method according to claim 1 which employs a mixed aqueous/organic solvent.
 4. Method according to claim 1 wherein said monomers, comprise one or more of substituted and unsubstituted monomers selected from the group consisting of paraphenylenevinylenes, anilines, azines, thiophenes, p-phenylenes, furanes, pyrroles, selenophenes, acetylenes, olefins and mixtures thereof.
 5. Method according to claim 1, further comprising a step of chemically modifying and/or doping.
 6. A method according to claim 1, wherein said mixture is coated onto a surface and said step (b) is carried out so as to effect photoinduced coating of said surface with the produced polymer.
 7. A method according to claim 6 wherein the coated surface is selected from the group consisting of glass, quartz, fluorocarbons, other synthetic polymers, and metals.
 8. The method of claim 1 wherein said oxidiser comprises one or more oxidiser selected from the group consisting of Cr₂O₇ ²⁻, MnO₄ ⁻.Fe(CN)₆ ³⁻, S₂O₈ ²⁻, B₄O₇ ²⁻, salts of Cu, salts of Co, salts of V, salts of Mo, salts of Ni, salts of W, salts of Fe, salts of Nb, salts of Ta, salts of Re, salts of Ru, salts of Ir, salts of Os and mixtures thereof.
 9. A microelectrochemical device comprising polymer prepared by the method of claim
 1. 10. A capacitor comprising a polymer prepared by the method of claim
 1. 11. A device comprising an electromagnetic and/or microwave interference coating comprising a polymer prepared by the method of claim
 1. 12. (canceled)
 13. A photorecording or photosensitive material comprising a polymer prepared by the method of claim
 1. 14. A sensor or assay system comprising a polymer prepared by the method of claim
 1. 15. An optical device comprising a polymer prepared by the method of claim
 1. 16. An optical device according to claim 15 wherein the device is a nonlinear optical device. 17-18. (canceled)
 19. A battery comprising a polymer prepared by the method of claim
 1. 